Fruits, 2015, vol. 70(4), p. 249-256 c Cirad / EDP Sciences 2015 DOI: 10.1051/fruits/2015022 Available online at: www.fruits-journal.org Original article Bio-agronomic characterization of twelve plum cultivars on two clonal rootstocks in a semi-arid environment in Sicily Filippo Ferlito1,2, Alberto Continella1, Elisabetta Nicolosi1, Biagio Dimauro3, Massimiliano Brugaletta1, Antonio Cicala1 and Stefano La Malfa1, 1 Dipartimento di Agricoltura, Alimentazione e Ambiente, University of Catania, Via Valdisavoia, 5 -95123 Catania, Italy 2 Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di Ricerca per l’Agrumicoltura e le Colture Mediterranee (CRA-ACM), Corso Savoia 190, 95024 Acireale (CT), Italy 3 Assessorato Regionale Risorse Agricole e Alimentari, Dipartimento Interventi Infrastrutturali, UOS Centro Colture Protette, Comiso (RG), Italy Received 28 June 2014 – Accepted 28 February 2015 Abstract – Introduction. Plum cultivation in Southern Italy is of great interest due to the possibility of obtaining produce over an extended period using early and late varieties. The objective of this study was to choose the best combination of cultivars and rootstock to make the production period as long as possible. Materials and methods. The r influence of two rootstocks i.e. Myrobalan 29C (Prunus cerasifera Ehrn.) and Montclar [Prunus persica (L.) Batsch] on growth, yield and fruit quality of nine Japanese and three European plum cultivars was evaluated. Results and r discussion. Four years after planting, the trees on Montclar rootstock displayed higher vigour. The highest yield was recorded on Shiro and Obilnaya grafted on both rootstocks. Black Amber produced the largest fruit and Obilnaya the smallest. Conclusion. This research contributed to identifying the most promising cultivars to be successfully grown in Southern Italy. Keywords: Italy / Sicily / European plum (Prunus domestica) / Japanese plum (Prunus salicina) / Myrobalan 29C r (Prunus cerasifera) / Montclar (Prunus persica) / fruit quality / rootstock Résumé – Caractérisation bio-agronomique de douze cultivars de pruniers greffés sur deux porte-greffes sous le climat semi-aride de Sicile. Introduction. La culture du prunier dans le Sud de l’Italie présente un grand intérêt par la possibilité d’étendre la période de production en utilisant une gamme de précocité variétale. L’objet de cette étude portait sur le choix des cultivars et des porte-greffes permettant de produire la plus longue période possible. Matériel r et méthodes. L’influence des porte-greffes ‘Myrobalan 29C’ (Prunus cerasifera Ehrn.) et ‘Montclar’[Prunus persica (L.) Batsch] a été testée sur la croissance, le rendement et la qualité des fruits de douze cultivars japonais et européen. r Résultats et discussion. Quatre ans après plantation, les arbres greffés sur ‘Montclar’ se sont montrés plus vigoureux. Les rendements les plus élevés ont été relevés avec ‘Shiro’ et ‘Obilnaya’ quelque soit le porte-greffe. ‘Black Amber’ a produit les prunes les plus grosses, tandis que ‘Obilnaya’ a produit les plus petits fruits. Conclusion. L’étude a contribué à identifier les variétés les plus prometteuses à recommander dans les régions du Sud de l’Italie Mots clés : Italie / Sicile / prunier d’Europe (Prunus domestica) / prunier du Japon (Prunus salicina) / Myrobalan 29C (Prunus cerasifera) / Montclar (Prunus persica) / qualité du fruit / porte-greffe 1 Introduction better adapted to many warm climatic regions for both early and late production as compared to the European plums [1]. Japanese (Prunus salicina Lindl.) and European plums (Prunus domestica L.) are amongst the most widely cultivated Among the regions potentially suitable for plum produc- fruit species in temperate climates. Their production for fresh tion in southern Italy is Sicily, characterized by hot and dry consumption has increased significantly in recent decades. summers, with its rainfall concentrated during the winter This has been due to both the expansion of the cultivation season. These climatic variables have a strong influence on area and the extension of the harvesting season by the adop- bud dormancy, growth activity and fruit ripening of decidu- tion of several Japanese cultivars. In fact, these cultivars are ous species. Nevertheless, previous trials with raspberry and apricot gave evidence of the possibility to cultivate low chill- Corresponding author: [email protected] ing cultivars in Sicily, even in the coastal areas [2, 3]. 250 Filippo Ferlito et al.: Fruits 70 (2015) 249–256 Phenology of woody plants is strictly dependent on the Ragusa district (lat. 36.97 N; long. 14.45 E; elevation 123 m). species [4], rootstock and variety combination [5], tree age [6] Nine Japanese cultivars (Sorriso di Primavera, Early Golden, and the interaction with other biotic and abiotic factors. As for Black Amber, Shiro, Red Beaut, Angeleno, Obilnaya, Black rootstock, it has been reported that they can have profound ef- Star and Friar) and 3 European cultivars (Stanley, Grossa di fects on scions. These effects include the control of tree size, Felisio and President) were planted in 2007. Each cultivar time of flowering [7], cold hardiness, disease resistance, and was grafted on two clonal rootstocks: Myrobalan 29C (Prunus r nutritional composition of the plant [8]. cerasifera Ehrh.) and Montclar [Prunus persica (Batsch) In warm climates the phenological phases are usually L.] except for Black Amber and Early Golden which were r shorter. Insufficient winter chilling can severely reduce yields. grafted only on Myrobalan 29C and Montclar, respectively. When chilling requirements are not fulfilled, the flowering of The soil in the study area is deep, sandy and well drained trees is irregular and delayed, leading to non-uniform crop with the following characteristics: pH 7.8; calcium carbon- development. This results in variable fruit sizes and maturity ate 7%; active calcium carbonate 0.8%; electrical conductivity stages and can substantially reduce yield [9]. 0.65 dS m−1 (1:5, 25 ◦C); and organic matter content 1.3%. For instance, a study on sweet cherry demonstrated that The trees were spaced 5 m between rows and 3 m within environmental factors such as photoperiod and temperature the rows. The rows were oriented North-South and the trees greatly affected bud opening and vegetative growth [10]. An were trained to an open vase with three main branches. Two earlier start of these phenological phases may have consider- identical plots, each containing 5 trees (10 trees per rootstock), able implications for both the risk of frost damage and photo- were arranged in a completely randomized design. Trees were synthetic activity [11]. subjected to standard cultivation practices and were irrigated Although the chilling requirements for plum have not been weekly from May to September. The total amount of wa- studied much, it seems that most varieties exhibit a behavior ter supplied was of about 200 mm ha−1 year−1. A traditional similar to that of peach. Yields can be reduced in warm regions fertilization regime was applied, with 60 kg ha−1 nitrogen, if the chilling hours are insufficient to break the rest period of 30 kg ha−1 phosphate and 90 kg ha−1 potassium. Phytoprotec- both flower and leaf buds [1]. tion was based on treatments with copper sulphate to control Okie and Hancock [1] report that most European plums re- leaf curl and other fungi, and with mineral oils combined with quire relatively high numbers of ‘Chilling Hours’ (CH) (proba- pyrethroids to control aphids. bly >1,000 h), whereas most Japanese plums need much fewer (∼500–800 h). The European plum, Prunus domestica, requires about 100 2.2 Climate variables and phenology to 200 more chilling hours than the Japanese plum, Prunus salicina [12]. After CH accumulation, bud burst requires high Daily temperature and rainfall data were provided by the temperatures defined as ‘Growing Degree Hours’ (GDH) [13]. Sicilian Agro-meteorological Information Service (SIAS). The Both CH and GDH accumulation models are important for chilling requirements for breaking the dormancy of each culti- forecasting the blooming and cross-pollination behavior of dif- var were calculated for a decade as CH [30]. Heat requirements ferent cultivars [14] and to predict the fruit growth rate, as were calculated as ‘growing degree hours’ (GDHs) according well as the ripening and harvest period [15]. ‘Chilling Hours’ to Richardson et al.[13]. For each cultivar, heat requirements is preferred to ‘Chilling Units’ in temperate zones as the lat- were calculated as the number of GDHs accumulated between ter is more suitable for cooler areas [16]. Temperature also the end of dormancy and bloom (50% open flowers). The main influences flower bud abscission [17], pollen viability and phenological phases [31] were monitored for two years. stigma receptivity [18], fertilization [19], fruit growth and shape [20, 21] and anthocyanin synthesis during fruit ripen- ing [22]. The study of climate effects is further complicated 2.3 Growth monitoring by the fact that rootstocks play a major role in the above men- ff tioned phenological phases [23]bya ecting tree growth, veg- To calculate the ‘trunk cross-sectional area’ (TCA) val- etative and reproductive behaviour [24, 25], fruit organoleptic ues, the trunk circumference was measured at 10 cm from the characteristics [26], antioxidant activity [27,28] and nutraceu- ground level. This was done at the bud dormancy phenological tical content [29]. Our research was undertaken to evaluate the stage (January 2010) and at the end of the harvest period (Oc- performance of three European and nine Japanese plum culti- tober 2011) and the percentage increase was calculated. Three vars on two rootstocks in a semi-arid climate in Sicily. Suitable fruiting shoots per plant were selected and their lengths and the cultivars are needed to extend the harvest season and to help number of buds were determined. The fertility index was ob- the industry adapt to the manifestations of climate change. tained as the ratio between the number of productive buds and the length of the fruiting shoots.